Envelope sealing closure and method of making it



' March 24, 1942. T, H, KRUEGER 2,277,116

ENVELOPE SEALING CLOSURES AND METHOD OF MAKING THEM Filed Oct. 6, 193s INVENT OR.

flwiffrueger ATTORNEY.

Patented Mar. 24, 19 2 UNITED. STATE S, PATENT OFFICE ENVELOPE SEALING CLOSURE AND METHOD or MAKING IT I Theodore H. Krueger, Shelton, Conn. Application October 6, 1938, Serial No. 233,513

2 Claims. (Cl. 229-80) This invention relates to envelope sealing closures and methods of making them and is herein illustrated as embodied in paper envelopes which may also be made of Cellophane or cellulose acetate or glassine;

Many dimculties have been encountered in satisfactorily sealing paper and especially viscose adhesive is described as'adaptedrto be applied to the paper, or other material of which the enand cellulose acetate envelopes. Usually a liqfingers or the envelope and leave a mess, and very often fail to seal the envelope properly, even velope is made, while the paper web is moving lengthwise. Some seams of the envelope are described as sealed by other adhesives otherwise applied. Theforegoing procedure makes possible the application of the heat-softened adhesive described below-one which can be most economically applied by means of a roll and doctor bar.

According to the present invention, mere pressure with a small hot implement gives a tight moisture proof seal. All the mess and slowness .of moistening gummed flaps is avoided. Ma-

chine-sealing of envelopes is made more dependable, and the sealing machines are greatly simpliiled. The whole operation'is more sanitary, and the preferred adhesive has no odor or taste and is non-curling and non-toxic.

Other features and advantages will hereinafter appear.

though the envelope appears to be properly sealed. If they put on too little solvent, the envelope is not sealed. Moreover, envelopes that get wet often open by accidental softening of the water-softened adhesive, and they may open during damp weather.

Heat sealed adhesives have not been used because of the dimculty in applying them, and also because many of them are expensive, and some of them require a heat high enough to scorch paper. Most of them could not be commercially applied to paper by printing processes with the result that they could not be applied in ordinary envelope-forming machines. could be applied when in solutionin some volatile inflammable solvent, thus introducing a'hazard in the envelope manufacture. Moreover, heatsoftened adhesives often failed to work properly, perhaps because most of them required a heat great enough to approach the scorching point of paper when they were softened, with the result that the paper was injured or the contents of the envelope or package was scorched, and the user was likely to be burned. Some heat sealing adhesives suchas plain paraflin give a bond which is too weak for practical use on envelopes.

According to the present invention these and other difllculties are overcome and. an envelope sealing closure is provided which is cheap, the envelope is easily maufactured, the seal is secure and yet made effective at a temperature which may be safe for the average worker to handle.

' To attain these and other ends the. heat sealing Some of them only The'accompanying drawing shows one form of envelope of the present invention.,

In the form shown the envelope It) was made from a continuous web of paper having its length lengthwise of the web, and in the form illustrated the sealing'stripe of adhesive I l of the envelope was put on in a continuous strip running longitudinally of the paper web. This web was run lengthwise between a hot roll and a doctor bar which applied a heat-softened adhesive material made as follows: Wax, such as paramne wax having a melting point of to 132 F., was

melted and 6% to 30% of a hydro-carbon gum such as thin sheets of pale crepe rubber R. C. M. A. not more than 0.04 inch thick was quickly immersed, in individual sheets, at 200 F... soakedfor fifteen minutes and agitated for two hours in a Warner-Pfleiderer class III type BB mixer. An age resistant, such as of hydro quinone could be added.

The roll and doctor bar were so controlled that the paper web from which the envelope was made carried the wide strip II of the adhesive along several longitudinal strips on the web. The envelope was then completed by die-cutting the blank so as to bring the proper strips on the edge, gluing and folding to form the seams l2 and I3, the seams l2 and I3 adhesive.

The stripe of heat-softened adhesive ll only covers part of the flap ll so that when the flap is folded down around the usual top fold I9 of the envelope, the lower edge is of the stripe ll now becomes the upper edge, and is below the being formed by anothertents of the envelope.

usual cutaway edge of the envelope when sealed down, thus avoiding any possibility of sealing the heat-sealed adhesive on to the con- The adhesive Ii usually is so adjusted in composition as to soften below 200 F. but above summer temperatures. One softening at about 160 F. is useful even in semitropical climates.

The envelope can be sealed by hot pressing the flap I4 down on the body ll of the envelope, either by a tool which might be electrically heated or by a mechanically operated device. Even some incandescent electric lamps may be used as a heating and closing iron.

For fine envelopes the edge ll of the flap formed by the edge of the web, may be too rough for fastidious users, and so the outer edge l8 of the flap is often cut to any desired formvor size, by a die as an incident to the manufacture of the envelope.

Having thus described one embodiment of the invention, what is claimed is:

1. An envelope having a' body including a flap soften to become adhesive below 200 P. so as to adhere to the body of theenvelope to seal it.

2. An envelope having a body including a flap held by a water-soluble adhesive, and a nearly rectangular closure flap carrying along its long straight edge a continuous strip of an adhesive scalable under heat and pressure to the body ofthe envelope, said last named adhesive containing a large proportion of paramne wax and less than one-third as much rubber and adapted to soften to become adhesive below 200 F. so as to adhere to the body of the envelope to seal it.

' THEODORE H. KRUEGER. 

